Modern semiconductor manufacturing generally relies on ion implanter systems for doping or otherwise modifying silicon and other types of semiconductor wafers. A typical ion implanter system performs the doping by generating an ion beam and steering it into a substrate so that the ions come to rest beneath the surface. As a part of this process it is often convenient to arrange that the ions travel through most of the implanter's optical system at the energy at which they were extracted from a source, but use electric fields near the end of the beamline to accelerate or decelerate the ions to the required implantation energy. Such an arrangement improves transmission efficiency.
High-current ion implanter systems are one type of implanter system that is widely used in semiconductor manufacturing. Such implanter systems typically produce currents up to 25 milliamperes (mA). An important class of high current implanter systems uses an expanded beam, also known as a ribbon beam. In high-dose applications, a higher beam current results in a faster implantation, which means a greater output of wafers per hour. Ion implanter system manufacturers have invested a great deal of effort in maximizing beam current, especially at the lowest energies, where Child's law limits the flux of ions that can be extracted from an ion source. Despite this effort, low-energy, high-current ion implanter systems generally operate with less precision than implanters known as medium current machines.
Medium-current ion implanter systems produce an ion beam having an intensity in the range of one microampere (μA) to about five mA, at energies between 5 kiloelectron volt (keV) and 900 keV. Generally, medium current implanter systems operate by scanning a spot beam across a wafer. In contrast to low-energy high-current ion implanter systems, medium-current ion implanters can operate with higher precision because beam scanning is used in place of a ribbon beam causing the beam to scan back and forth very quickly across the wafer. However, when the ion beam energy is decreased, the spot size typically increases, making it harder to use a medium-current ion implanter for scanning.
In order to meet the increasing demands of semiconductor manufacturers to place more components on an integrated circuit, it is necessary that future high-current ion implanter systems and medium-current ion implanter systems provide greater capability in controlling the ion beam so that lower energies can be produced. Controlling the ion beam at lower energies will allow ion implanter systems to deposit ions at smaller depths and dimensions below the wafer surface and consequently place more components onto an integrated circuit.
Therefore, in order to meet the increasing demands of semiconductor manufacturers, there is a need for providing a high-current ion implanter system and medium-current ion implanter system that can better control an ion beam. An even better scenario would be to provide a single ion implanter system that can control an ion beam at lower beam energies and simultaneously perform the functionalities of both high-current ion implanter systems and medium-current ion implanter systems.